Because I think i can show how the idea of time is unfounded, I read the excellent paper 'forget time', and because I think it may be over complicated in places, I composed this response... (It turned out to be rather detailed, so I posted a cut down version on my own Amazon forum, so as not to 'bomb' someone else's forum

“Forget Time” (Essay for the FQXi competition) is in my opinion excellent, but perhaps over complicated in places, and perhaps clings to the idea of ‘trying to explain how Time may not exist... in terms of ‘Time’, which may disempower some of the points it makes.

I suggest this because I have certain differing points of view about a number of the long held scientific beliefs or assumptions it draws on, and the possibility that in our understanding of even basic mechanics there may be some very significant, yet long hidden oversights, conveniently summed up in the works of Galileo, Newton and Einstein, thus,

P1: Galileo Galilei,

Section III-A (of ‘forget time’ starts

“Clock making owes a lot to Galileo Galilei, who discovered that the small oscillations of a pendulum are isochronous.”... “Using his own pulse”

My problem here is the word “isochronous” (wiki – “from the Greek iso (equal) and chronos (time). It literally means regularly, or at equal time intervals.)

This suggests that Time in some way exists, and that Galileo discovered that any particular pendulum will “take” the same amount of “time” to complete each oscillation. And that ‘intervals’ ‘of Time’ also exist.

I suggest (from all I have read) that Galileo did not observe, or prove, that there exists a ‘Future’. And that he did not observe, or prove, that there exists a ‘Past’. And that he did not observe, or prove, that there exists a thing called ‘Time’ which ‘passes’ (from ‘the Future’ to ‘The past’) as pendulums oscillate, or as anything else moves. Nor did he prove that ‘intervals’ or durations etc really ‘exist’, or make any sense other than as useful ideas..

These details may seem trivial, or a case of being too critical too soon in a matter, here, but unless the existence of these ‘things’ is proven, then it is very unscientific, and will almost certainly lead to deep confusion (as we will see) if they are built on as if they are in any way confirmed – while never actually confirming them, before we reach apparently solid conclusions based on them.

Thus, IMO (In My Opinion) Galileo did not actually prove pendulums were ‘isochronous’, He only proved that pendulums can swing, human bodies can ‘pulse’, and that these two things can be compared, and found to ‘align’, i.e. Unexpectedly - for each pendulum swing, even though its amplitude decreases, a pulse may consistently complete 5 beats.

This is not IMO a trivial reworking of the initial term ‘iso-chronous’, because this word suggests and implies, without proving it, that ‘Time’ and thus in some way ‘The past’ and ‘The future’, along with times ‘flow’, ‘direction’ and ‘function’ (allowing or making things happen) all in some way exist. But none of these ‘things’ have been observed (By Galileo etc) All that is observed is matter, gravity, motion, and energy etc can exist, and thus things can move and be compared ‘in a human brain’.

P2, “Isaac Newton

III A continues,

“Isaac Newton provides a nice clarification of this issue in the Principia. According to Newton, we never directly measure the true time variable t. Rather, we always construct devises, the “clocks” indeed, that have observable quantities (say, the angle _ between the clock’s hand and the direction of the digit “12”), that move proportionally to the true time, “

(my underlining)

The problem here is that we do indeed construct devices, which do indeed provide a ‘useful example of regular motion’. Useful because we can sensibly compare other complex motion to it. But, as above, as far as I am aware, Newton provided very useful equations for how gravity accelerates falling objects etc, but Newton did not observe, or prove, that there exists a ‘Future’. Or that there exists a ‘Past’. Or that there exists a thing called ‘Time’ which ‘passes’ (from ‘the Future’ to ‘The past’) as objects fall and accelerate to Earth.

E.g. If we take any example of Newton’s equations for a falling body, apparently revealing say that ‘a stone takes 5 seconds to fall down a well’, this can be seen to only prove that stones fall and accelerate, and that the Earth spins, and for said fall the Earth spins through 0.016... ‘degrees’.

In other words, the accuracy and usefulness of Newton’s equations in no way also actually prove that a thing called ‘time’ also exists and is ‘needed’ or has a ‘fixed direction’ in which it ‘passes’ as stones fall etc. The equations only show that things can exist and move and this motion can be compared.

P3 Einstein, Relativity.

‘Forget Time’ - P I THE NEED TO FORGET TIME ) starts by saying,

“General relativity has changed our understanding of space and time”.

But this suggests that the existence of time was either proven before Einstein’s work, or that Einstein’s work in some way proved times existence.

Simultaneity

IMO, In Einstein’s ‘Electrodynamics’ 1905, he says,

...we must bear carefully in mind that a mathematical description of this kind has no physical meaning unless we are quite clear as to what we understand by “time.” ... If, for instance, I say, “That train arrives here at 7 o'clock,” I mean something like this: “The pointing of the small hand of my watch to 7 and the arrival of the train are simultaneous events.”3

This is not a logical proof that time exists etc, it is a description of how things are if one ‘assumes’ that time exists. In other words, all Einstein has shown here is that objects can exist and move if they have the energy to do so. E.g. ‘Trains’ can move, and ‘motorised hands’ can ‘rotate around numbered dials’, and that one can choose to compare the positions of moving objects.

Very explicitly Einstein has not proved, or (pointed to a proof) that that there exists a ‘Future’. Or that there exists a ‘Past’. Or that there exists a thing called ‘Time’ which ‘passes’ (from ‘the Future’ to ‘The past’) as trains move, (or stop), as motorised hands rotate, or as humans choose to compare the motion or positions of these things. He has also not proven that extra to energy, the existence and passage of ‘time’ is needed for things to be able to move, and be compared etc. Or that because the ‘clock’ hand has been manufactured to rotate in one fixed direction, that this relates to or proves that ‘time’ also exists, and, generally ‘flows’ in ‘one fixed direction’.

P III. MECHANICS IS ABOUT RELATIONS BETWEEN VARIABLES, SAYS,

“The Relativity revolution has modified the notion of time in a number of ways. I skip here the changes introduced by Special Relativity (in particular, the relativity of simultaneity), which are much discussed and well understood,”

(my underlining)

However, as with the above, IMO, along with not proving the existence of function of time and in particular not proving ‘the past’ or ‘future’ exist, Einstein has also not proven that ‘this moment’ is a fleeting or passing thing, or that there may be ‘different moments’.

Thus the term ‘simultaneous’ (same-time) is seriously questioned. I.e. the train or the watch hand (or any other things) may just ‘always’ be somewhere, doing something, and that is it! I.e. Einstein has not shown that ‘time’ or ‘different times’ exist, the word simultaneous can be seen as redundant and meaningless. And perhaps everything is always just doing something ‘now’. Any ‘thoughts’ to the contrary, will actually, in fact, just be the matter in your brain, ‘doing something now’. i.e I think the ‘relativity of simultaneity’ is not well understood.

‘Simultaneity’ and ‘Time’ dilation.

Issues around simultaneity are often expressed by the statement ‘moving clocks run slow’. This has been scientifically confirmed, but that extra to showing ‘how energy can be released smoothly’, a ‘clock’ also proves or reveals the nature of a thing called ‘time’ has not IMO been proven.

Thus it is accepted as true that if one ‘clock’ travels far and fast, away from and back to a similar stationary device, the hands on the travelling device will show fewer degrees of rotation that the stationary device. And thus that less ‘local change’ has occurred to the travelling device. (Corresponding to more ‘change in location’ of the device).

But it is not accepted that this experiment (as actually carried out via GPS etc) also proves that ‘time’ exists, and flows in one direction, and is needed for motion or change, or that the moving device ‘sinks’ in some way into ‘the past’. Or its counterpart rushes into ‘the future’ more freely. It only proves that moving things may ‘change’ more slowly than others.

General Relativity.

Thus IMO even GR does not prove the existence of, or say anything about ‘Time’. It does brilliantly reveal how mass warps space, how gravity slows ‘change’, and how ‘change in location’ and ‘local change’ are interrelated. Or to be more precise, simply the same thing.

P4,

Section VI. RECOVERY OF TIME, suggests,

“If we formulate the fundamental theory of nature in a timeless language, we have then the problem of recovering the familiar notion of time”.

(my underlining) I disagree because the notion of time has not been proven to be valid - other than as a useful semantic tool for understanding, describing, comparing and making calculations about all the constant ‘change’ around and within us. However, part of the problem of recovering the notion of time is put as...

The time of our experience is associated with a number of peculiar features that make it a very special physical variable.

"Intuitively (and imprecisely) speaking, time “flows”, we can never “go back in time”, we remember the past but not the future, and so on. Where do all these very peculiar features of the time variable come from?"

"I think that these features are not mechanical. Rather they emerge at the thermodynamical level". (my underlining)

Building on my previous reasoning, if it is basically correct, then...

‘Time’ is not a special physical variable, it is a useful idea, and the word we may give to one sample of motion (usually taken from a smoothly moving/rotating body or machine) we use to compare to another. The idea time flows, however loosely taken, is just the observation that things are here now, and they move and change. If anything can be said to flow it can be matter (water etc) and energy, heat light, electricity etc. We may pick various examples of movement/energy, and choose to call the direction it moves ‘forwards’ but this doesn’t prove ‘time’ really ‘exists’ or ‘flows’. (and if doesn’t exist, or flow etc, it doesn’t need to be explained, or explained away!

We can’t “go back in time”, because the existence/function of Time, or even an initial reason for suspecting its existence has not been shown.

‘Back in time’ suggest ‘the past’, + the idea “we remember the past but not the future,”.

Here we need to be extremely clear as to what we mean by these terms. Ask anyone about ‘the past’ and they will tell you something about ‘the physical contents of their minds’ (here, now) or objects they ‘call’ artefacts, also ‘here now’.

We may assume, or declare that these things ‘also’ relate to or prove the existence of ‘the’, ‘temporal past’ – but all these things prove is that matter can exist, and interact, creating intricate ‘matter in-formation’ in certain places. Thus we do not remember the (temporal) past. We look in our minds etc, and we CALL what we see ‘the past’.

Likewise we can create images or ideas in our minds e.g. ‘of a bridge collapsing, or not’ and we can CALL these ‘the future’, and say we can guess at, but not ‘remember’ ‘it – the future’. But again all we have proved is that matter within and with-out of us, can exist, move, and be compared etc. We have not proved that ‘time’ exists, and the ‘future’ exists, or that ‘time’ steadily brings ‘the future’ to us. Thus I think these things (the past and future) are absolutely no more than ‘labels’ we give to different types of thoughts, and invalid ‘things’ we think these thoughts relate to or prove. Thus IMO these features are not thermodynamical, because they don’t exist.

The ‘Arrow(s) of Time’ – the conflict between Classical and Quantum mechanics.

Thermodynamics, brings us to the supposed ‘arrow of time’, i.e. proof that there is something fundamentally one way in the workings of the universe. These may be said to be the ‘Thermodynamic’, ‘psychological’ and ‘cosmological’ arrows.

However, IMO, based on the above reasoning, in brief.

‘Thermodynamically’, cups of coffee get cold, and dropped vases smash, but we don’t typically see the opposite. This is true, but it does not prove there is a record of all events created and stored ‘behind’ them in a ‘temporal past’ nor that ‘time’ or a ‘temporal future’ exist.

‘psychologically’ we may walk around the earth, light hitting our eyes, and us sequentially organising ‘piles’ of data if you will.

And ‘cosmologically’ the universe may in general be expanding in all directions unstoppable – heading for a heat death. (or doing anything else).

All of these things may be true, but IMO none of them prove there is a ‘record of all events’ created and stored ‘behind’ us in some way in fourth dimension or ‘temporal past’. Nor that as things move and change they need a ‘future’ in which to head into. Nor that extra to energy, a thing called ‘time’ passes and is needed for things to change. Nor that this ‘time’ thing has fixed, or otherwise, ‘direction’. Nor that it can be slowed or warped (‘rates of change’ can be slowed – but that’s not a proof of past/future etc).

IMO, all of the above are projections, of (a very useful) framework of ideas, on to what we actually observe. And confusion arises wherever we forget that we just made up these useful terms, and instead start actually looking for, or thinking we have to ‘actually’ prove or disprove, the past, the future, time, or its ‘direction’ etc.

Ultimately the problems seems to be –

1- IF we assume TIME exists, THEN the world seems to confirm our ASSUMPTION

2- BUT, IF we assume things JUST exist and interact, then this too will seem to be confirmed

The difference between these 2 views is, #1 depends on the existence of numerous unseen unproven intangible ‘things’ (past future etc), while #2 depend solely on countless things that we can constantly see, detect, measure, use and compare etc =)

RE the conflict between Classical and Quantum mechanics – re Time.

The apparent or suggested ‘conflict’ between Classical and Quantum mechanics, re Time is as I understand it the conflicting idea that Time seems to have an arrow, or fixed direction on a large scale (Newtonian/Einsteinium Relativistic physics), but on a Quantum mechanical level processes can operate perfectly ‘forwards’ or ‘backwards’ – suggesting ‘time does not exist’ on this scale, or that ‘time is reversible’ on this scale.

IMO, this confusion is based entirely on the misunderstandings I thing I have exposed above. Thus, while it may be true that on a large scale dropped vases smash into fragments, but fragments don’t fly up to form vases – and on a small scale, one particle may disintegrate into others AND the process may occur in reverse perfectly – this is just because that IS the way matter behave on small or large scales. As large aggregates of matter are splitting in a ‘one way’ manner (vases smashing), within those fragments (or elsewhere) minute particles may be splitting and reforming perfectly.

But this IM can have nothing to do at all with a thing called ‘time’ existing, and ‘it’ behaving in different ways on different physical scales. Because ‘times’ existence has only ever been wrongly assumed, and not proven – and it must scientifically be very wrong to try and force the idea to work in quantum mechanics if it can’t even be shown to work with a large scale ‘pendulum’.

Note, this is not a cop out, IMO, though I know very little about QM, I feel sure that trying to understand it while also trying to force invalid assumptions to ‘fit’ within it must obscure any problems, and if the ‘concept being incorrectly forced in is a complex and ethereal as ‘time’ then this must almost certainly have a very detrimental effect on understanding.

Conclusion. There’s no need to ‘forget time’.

So, in conclusion, Mr Rovelli, IMO there is no need to ‘forget time’, just to remember that we made the idea up, but many people don’t seem to realise this. Instead, I believe (mysterious and amazing as it is) that things are just as we directly observe them to be, matter exists, moves and interacts, possibly ultimately heading, on average, towards a universal heat death etc, but always just doing it, in countless real, physical directions, ‘now’ – to use a redundant term.

RE Quantum gravity, as I say I know very little at all about QM, but I feel sure (if I am right) that first pulling out time from any understanding of QM in relation to ‘time’ seeming to exist, or not exist or be reversible, or not, etc on different scales may help. Then considering how Newton did not show how apples fall under gravity ‘with time’, but just that their falling can be compared to other motion. And how Einstein did not (IMO) show time exists, nor that it is merged with space, nor that ‘time’ has a direction or can be dilated etc, may open up some ‘paradigm shifts’ in ways to look at QM and Quantum Gravity.